Polyesters utilized in fiber formation are generally produced by a heated reaction of one or more dibasic acids such as terephthalic acid, or the like, with one or more polyhydroxy compounds such as ethylene glycol, propylene glycol, 1,4-cyclohexane dimethanol, or the like, until a product of desired viscosity is obtained. The formed polyesters are characterized in that they contain both terminal hydroxy and carboxy groups. Terminal hydroxy groups are generally more predominant due to the incorporation of an excess of polyol in the reactive mixture.
Polyesters are of great importance in the manufacture of tire cords, and as reinforcement for belts, hoses and many other useful articles. In many of these commercial applications the presence of excessive carboxyl groups in the polymer molecule is detrimental.
Previous attempts at acid group reduction in polyesters have resulted in a loss of average molecular weight in the polyester product due to substantial cleavage in the polyester backbone.
It is an objective of the instant invention to provide improved polyester materials in which the pendant carboxyl groups are either greatly reduced in number or are completely removed.
It is a further object of the invention to endcap free carboxyl groups on polyesters without producing water as a byproduct and while maintaining the molecular weight of the polyesters.
It is a further object of the instant invention to provide polyester materials having reduced sensitivity to water.